The present invention relates to a method of producing a rare earth bond magnet (anisotropic) which uses as a raw material rare earth alloys prepared by a rapid cooling thin belt forming method, (melt quenching method) and more particularly, the present invention is directed to a method of producing an anisotropic rare earth bond magnet of scaly shape which has a vertical magnetic anisotropy relative to a pressing surface by heating a raw material of rare earth alloys and pulverizing and pressing it by the addition of an external stress. The magnet material as described is suitable for the production of a resin-impregnated bond magnet having a magnetic anisotropy.
Further, the present invention is directed to a method of producing a rare earth bond magnet in which magnet powder material composed of a rare earth alloy is mixed with non-metallic inorganic binders and the mixture is subjected to molding and then treated by a low temperature heat treatment so that the crystal shape thereof is not changed, wherein the particles of the powder material are bonded to each other by the resolved binders.
The rare earth bond magnets which have been on actual use are generally classified into Sm-Co magnets and Nd-Fe-B magnets, and the Nd-Fe-B magnets are produced by forming amorphous ribbons by rapidly cooling (or melt quenching) a melted alloy, followed by a heat treatment and pulverization to thereby provide a desired powder material. This powder is anisopropic and an anisotropic bond magnet can be formed by using the same, as disclosed by Japanese Patent Publication (Unexamined) No. 59-64739.
Japanese Patent Publication (Unexamined) No. 60-100402 discloses the production of powder having magnetic anisotropy, in which the amorphous ribbons are pulverized and then heat pressed to form moldings (molded products). Thereafter, the molded products are heat-pressed at about 750.degree. C. and compression-molded to extend them in the lateral direction, and at this moment, crystal organization is arranged to provide a magnetic block having a magnetic anisotropy. Then, the magnetic block is pulverized to form powder of anisotropy.
However, in order to produce the magnetic anisotropic powder by means of the conventional method, it requires a compressive molding at a high temperature and an extention operation in an inert gas atmosphere. This requires a substantial length of time and, therefore, results in substantial reduction of productivity. Further, the thus produced anisotropic block has a very high hardness which presents difficulty in pulverization.
In order to solve the problems of pulverizing the anisotropic blocks, an attempt has been suggested to repeatedly absorb and discharge hydrogen to thereby granulate the block material. In this method, however, the resultant shape of the powder is influenced by the crystal shape of the ungranulated anisotropic block. Further, this method is disadvantageous in that particle size distribution of the powder is scattered largely, with the result of unstable properties of the bond magnets.